1. Field of the Invention
The present invention relates to an airbag apparatus for a front passenger seat adapted to be mounted on an instrument panel located in front of a front passenger seat of a vehicle. Particularly, the invention relates to an airbag apparatus for a front passenger seat that includes an airbag, an inflator for feeding an inflation gas to the airbag and a case for housing the airbag and the inflator.
2. Description of Related Art
As disclosed in JP2006-103654, JP2008-62710 and JP2008-254500, a known airbag apparatus for a front passenger seat includes an airbag that is deployable into a generally square conical contour whose front end is the top of the square cone, and includes a passenger side wall which is deployable at the rear end generally vertically and toward a front passenger seat, a circumferential wall which extends forward from the peripheral edge of the passenger side wall while tapering and converges at the front end, a gas inlet port located proximate the front end and at a generally center in a left and right direction of the airbag as inflated for introducing an inflation gas, and a recessed area that is sunken forward and extends vertically generally at the center in a left and right direction of the passenger side wall. The conventional airbag is formed by jointing peripheral edges of base materials, thus the circumferential wall has a seam that extends forward from the recessed area in the passenger side wall. This airbag is folded up to be reduced in size and mounted on the case by the peripheral edge of the gas inlet port, together with the inflator, and housed in the case.
Because of the seam that extends generally in a front and rear direction at the center in a left and right direction of the circumferential wall, the airbag as folded up has a bulky portion formed by multiple layers of the seam. Especially, the airbag apparatuses for a front passenger seat disclosed in JP2006-103654 and JP2008-254500 have another seam of base materials on the passenger side wall as well, respectively. The seam constitutes the leading end (or bottom) of the recessed area. Accordingly, the airbag has the seams over a generally entire circumference in a front and rear direction except the peripheral edge of the gas inlet port. Together with seam allowances comprised of the base materials, the seams form a bulky portion at the center in a left and right direction when folded up in layers when the airbag is folded up to be housed in the case. This bulky portion is located adjacent to the inflator in a case when the airbag and inflator are mounted on a case, which makes it difficult to store the airbag and inflator in a limited space of a case.
Thus, the conventional airbag apparatuses had a room for improvement in mounting in a limited space.